OYSTOSPERMEiE.

181

Important division of the freshwater Conferva , the Conjugates,in the species of which the filaments are flexible, mucous,and shining in the highest degree: in them, too, the fila-ments never taper, but are always exactly cylindrical. More-over, the articulations differ in the two groups : in the Cysto-spermece they are strongly marked, and when dried, becomecontracted and dark, while in the Conjugates they are faintlyindicated; and in dried specimens are often with difficultydiscoverable.

Such are the leading features of this interesting divisionof the Conferva, and on a careful examination and estima-tion of the many points of difference here enumerated be-tween them and the Conjugates, the tribe to which they mostclosely approximate, there can be no doubt, I apprehend,of the propriety of retaining them in a separate family.

The differences are too great to admit of their holdingmerely a generic rank. The naturalness of the differentgenera forming the preceding family may be readily per-ceived, these passing through certain species, the one intothe other; and all being allied by certain resemblances:but how wide is the interval between any of these and thegroup of Cystospermea !

The sporangia in the different species of Cystospermea areproduced in the same manner as in the non-conjugatingZygnemata; that is, by the concentration of the contentsof two adjacent cells in the same filament, this being neces-sarily always accompanied by the inflation of the receivingcell, and the giving cell being constantly placed in com-munication with the narrow end of the ovate inflated cell.

In all the Conjugates the endochrome is seen to pass throughtubes of connection between the cells, whether in differentor in the same filaments : in these, however, no such passagesexist, the contents of the cells escaping apparently througha rent occasioned by some agency in their extremities. Thenotice of this particular furnishes an additional distinctivecharacter between the two groups: but others still remain,two of which may next be noticed.

The first of these relates to the presence of a peculiar and